On 29 March 2017, the British Government, with the permission of Parliament, officially launched the withdrawal process, citing Article 50 of the Treaty on european Union. May called for early parliamentary elections in June 2017, which resulted in a minority Conservative government backed by the Democratic Unionist Party (DUP). Negotiations on the withdrawal between Britain and the EU began at the end of the month. The UK has negotiated the exit from the customs union and the single market. This led to the November 2018 withdrawal agreement, but the British Parliament voted three times against ratification. Labour wanted a deal to maintain a customs union, while many Conservatives opposed the financial settlement of the agreement and the “Irish backstop” to prevent border controls between Northern Ireland and the Republic of Ireland. The Liberal Democrats, the Scottish National Party (SNP) and others have tried to nullify Brexit with a second referendum. The political declaration provides that the EU-UK agreement on future relations will essentially be an economic and security partnership. In accordance with the political declaration, the 27 EU Member States agreed on 25 February 2020 on the negotiating mandate of the European Commission, which is negotiating on behalf of the Member States on future relations between the EU and the UNITED Kingdom. On this basis, the EU`s chief negotiator, Michel Barnier, presented in mid-March a draft comprehensive agreement on the new partnership with the UK, to which other elements were added. You can find this and the others on the UK Task Force`s website. The transition period is not extended.
The United Kingdom has stated that it does not want an extension. The option of an extension was included in the withdrawal agreement. The UK and the EU have had until 1 July 2020 to agree on a possible extension. EU leaders approve the postponement of the date of Brexit to 31 January 2020, or earlier, if the UK and European parliaments approve the withdrawal deal by then. The new relationship between the EU and the UK begins, provided an agreement has been reached, approved by the EU Member States, the European Parliament and the British Parliament. This is the third time the British Parliament has rejected the agreement. The United Kingdom has until 12 April 2019 to decide what to do next: on the issue of the Irish border, there is a protocol on Northern Ireland (the “backstop”) that is attached to the agreement, which defines a back case position that will only come into force if effective alternative regimes are not demonstrated before the end of the transition period. In this case, the UK will eclipse the EU`s common external tariff and Northern Ireland will stick to aspects of the internal market until such an event is carried out.
Neither party can unilaterally withdraw from this customs union. The aim of this backstop agreement is to avoid a “hard” border in Ireland, where customs controls are needed.  The United Kingdom triggers Article 50. This means that negotiations on the UK`s withdrawal from the EU can begin.